Hardening photographic emulsion



til) Patented May 11, 1937 UNITED STATE-s PATENT OFFICE HARDENING rno'rocnarmc EMULsroN Application September 10, 1936, Serial No.l00,137

15 Claims.

This invention relates to hardening agents for photographic gelatin and emulsions', and to a method for hardening such gelatin and emulsions.

A number of agents for hardening photographic gelatin or emulsions have been suggested in the literature. These include dialdehydes and bromine derivatives of monoaldehydes, such as dibromacrolein. Some of the hardening agents previously suggested have a tendency to fog a sensitive photographic emulsion, and in determining the utility of the various hardening agents, the melting point of the gelatin is ordinarily taken as the criterion of the hardening l5 action produced.

I have 'found that the halogen-substituted aldehyde acids are useful for hardening photographic gelatin and emulsions. lThese compounds do not fog a photographic emulsion, and permit processing of the emulsion at elevated temperatures. I have not relied upon the melting point produced by addition of my hardening agents to the emul` sion, buthave tested them by carrying out the photographic processes including developing,

rinsing, xing and washing at high temperatures to determine the ability of the hardening emulsion to withstand processing at these high temperatures, since thistest is obviously more signiicant.

In the accompanying drawing, Fig. `1 is an enlarged sectional view of a lm having a hardened emulsion made according to my invention, Fig. 2 is an enlarged sectional view of a lm having a hardened inter-layer and a hardened lter layer, and Fig. 3 is an enlarged sectional view of a lm. having a hardened anti-halation backing layer.

In the practice of my invention', the compounds used are incorporated in the gelatin or emulsion 40 by dissolving them in a suitable solvent which does not adverselyaifect the sensitive photographic emulsion, and mixing the solution of the hardening agent with the gelatin or emulsion. lThe compounds which I use for hardening the gelatin comprise the halogen-substituted aldehyde acids, such as mucobromic and mucochloric acids. The formulae for these compounds are as follows:

' Mucobromic acid:

cnr-Coon Br--ono Mucochloric acid:

cci-Coon Cl-oHo 'I'hese compounds may be produced according to the procedure of Simonis. Beriehteder Deutschen Chemischen Gesellschaft, vol.y 32, (1899), page v2084.

The following examples illustrate methods of incorporating the hardening agents in photographic emulsions according to my invention.

Example I To about 10 cc. of ethyl alcohol there was .added 0.05 gram of mucobromic acid to form a solution of the acid Vin alcohol. This solution was added to 225 grams (about 215 ce.) of a high speed, high contrast photographie emulsion (containing about '7% gelatin). After mixing the solution of the hardening agent with the emulsion, the mixture was immediately coated on a suitable support, such as a transparent cellulose acetate support, and permitted to dry. A similar emulsion to which no hardening agent had been added was also coated on a support and permitted to dry in a similar manner. These emulsions were then exposed and 'subjected to development, rinsing, fixing and washing at 85 F. Observation of the resulting plates showed that the emulsion to which the mucobromic acid had been added had a very denite increase in hardening over the control, and was not 'iogged vEafcmtple II A To about 10 ce. of ethyl alcohol there 'was added '0.1 gram of mucochloric acid to form a solution of the acid in alcohol. This solution was added to 225 grams of a high speed, high contrast photographic emulsion (containing about 7% gelatin), and after mixing the: solution of the hardening agent withl the emulsion, the emulsion was coated on a transparent cellulose acetate support. A similar emulsion to which no hardening agent had been added was coated on a support, and the two emulsions were exposed and processed including development, rinsing, xing and washing at both 85 F. and 100 F.

The emulsion to which no hardening agent had been added was quite soft at 85 F. and started to melt during development at F. The emulsion to which the hardening agent had been `added withstood processing at 85 F. quite satisfactorily, and although it was somewhat soft when processed at 100 F., it did not melt as did the control sample.

-Example III To about 25 cc. of ethyl alcohol there was added 0.4 g. of mucochloric acid to form a solution of the acid in alcohol. This solution was added to 250 g. of a gelatin solution consisting of '7 percent gelatin by weight. The gelatin solution containing mucochloric acid was coated on a transparent cellulose acetate support. A similar Vgelatin solution to which no hardener had been added was coated on a support, and the two exposed to processing at high temperatures. It was found the latter showed very bad swelling tendencies with the formation of a delicate surface easily susceptible to scratching, whereas the former presented a much more tough and durable surface during processing and resulted in a more satisfactory product when dried.

Example IV A hardened lter layer was made as follows:

v Over a hardened photographic emulsion coated on one side of a transparent support, there was coated a dyed gelatin layer containing mucochloric acid and having the following corn-v position:

Grams Gelatin solution (5% gelatin) 100 Congo red dye 2 Mucochloric acid .024

This coating was permitted to dry and was found to present a tough and durable surface when the lm was processed at high temperatures.

Example V A hardened anti-halation hacking layer was made as follows: A gelatin solution was made up containing gelatin, hardener, and dye in the following amounts:

Grams Gelatin solution (5% gelatin) 100 Mucochloric acid .12 Anti-halation dye 2 This solution was coated on the back of a cellulose acetate support and permitted to dry.

l jected to a similar incubation test.

The amount of hardening agent used, according to my invention, may vary from about 0.1 percent to about 0.5 percent of the weight of the gelatin in the emulsion. The hardening agent may be added to the gelatin used to produce the emulsion at some stage before emulsiflcation, or to the emulsion itself prior to coating. The hardening agents of my invention may also be mixed with gelatin to be used as layers other than emulsion layers \on the photographic supportfsuch as backing or anti-halation layers, or inter-layers coated between emulsion layers or between emulsion layers and support. For interlayers, the amount of aldehyde acid may vary from about... 0.1% to about `0.5% of the weight of the gelatin, while foibacking and anti-halation layers the amount may vary from about 0.4% to about 3.0% or more.

When the hardening agents which I contem'- plate using are added to certain photographic emulsions, a decrease in sensitivity results. Ihis is apparently due to a lowering of the pH of the emulsion by the acid used as a hardening agent.

. For this reason inemulsions with a pH of more than 7, it is advisable to use a salt of the acid hardening agent and to adjust the pH of the soluor other salts of the halogen-substituted aldehyde acids may be used. 'Ihese include salts of organic alkalis, such as triethanolamine, -diethylaminoethyl alcohol, or morpholine, as well as metallic salts.

In Fig. 1 of the accompanying drawing, which is an enlarged sectional view of a lm made according to my invention, I0 represents a transparent support of glass, cellulose acetate, or other suitable material coated with an emulsion layer II consisting of a gelatine-silver halide 'emulsion hardened with a halogen-substituted aldehyde, such as mucobromic or mucochloric acid.

In Fig. 2, which is an enlarged sectional view of a film used in three-color photography, I0 represents a transparent support of cellulose nitrate, cellulose acetate, cellulose acetate propionate, or other suitable material, having emulsion layers I2 and I3 on one side thereof, and emulsion layer I4 on the opposite side thereof. Between emulsion layers I2 and I3, there is a hardened gelatin inter-layer I5, and over emulsion layer III there is a hardened gelatin filter layer I6.

Fig. 3 shows a iilm having a hardened antihalation layer I8 coated on the back of support II), and emulsion'layer I 'I on the face of the support.

It is to be understood that other layers, such as subbing layers and non-curling layers may be added to the photographic element within the scope of my invention.

The halogen-substituted aldehyde acids are soluble in various solvents which may be used to incorporate the acid in the gelatin or emulsion. These solvents include water, the alkyl alcohols, and lower esters. Any other suitable solvent which does not adversely affect the gelatin or emulsion may also be used.

The examples and compounds included in the above specification are to be taken as illustrative only, since my invention is to be considered as limited only by the scope of the appended claims.

What I claim is:

1. Ariotographic element comprising a gelatin layer containing as a hardening agent a halogensubstituted aldehyde acid compound.

2. A photographic element comprising a gelatin layer containing as a hardening agent a halogensubstituted aldehyde acid.

3. A photographic elementlcomprising a gelatino-silver halide emulsion layer containing as a hardening agent a halogen-substituted aldehyde acid compound.

4. A photographic element comprising a gelatino-silver halide emulsion layer containing as a hardening agent a halogen-substituted aldehyde acid.

5. A photographic element comprising a gelatino-silver halide emulsion layer containing as a hardening agent mucobromic acid.

6. A photographic element comprising a gelatino-silver halide emulsion layer containing as a hardening agent mucochloric acid.

'7. The methodof hardening a photographic gelatin, which comprises incorporating therein a halogen-substituted aldehyde acid'compound.

8. 'Ihe method of hardening a photographic gelatin, which comprises incorporating therein a halogen-substituted aldehyde acid.

9. The method of hardening a gelatina-silver halide emulsion which comprises incorporating therein a halogen-substituted aldehyde acid.

10. 'I'he method of hardening a gelatine-silver 75 halide emulsion which comprises incorporating therein mucobromic acid.

l 11. The method of hardening a gelatino-silver halide emulsion which comprises incorporating therein mucochloric acid.

12. The method of producing a hardened gelatino-silver halide emulsion layer which comprises mixing an alcoholic solution of a halogen-substituted aldehyde acid with the emulsion, and coating the mixture on a support.

13. The method of producing a hardened gelatino-silver halide emulsion layer which comprises adding to a gelatina-silver halide emulsion about` 5 percent by volume of an alcoholic solution containing about 0.2 percent of the weight of the gelatin in the emulsion of a halogen-substituted aldehyde acid. and coating the mixture on a transparent support.

14. The method of producing a hardened gelatino-silver halide emulsion layer which comprises adding to a gelatine-silver halide emulsion about 5 percent by volume of an alcoholic solution containing about 0.3 percent of \`the\weight of the gelatin in the emulsion of mucoboinic acid, and coating the mixture on a transparent support.

15. The method of producing a hardene` gelatino-silver halide emulsion layer which co prises adding to a gelatino-sllver halide emulsion about 5 percent by volume of an alcoholic solution containing about 0.5 percent of the weight of the gelatin in the emulsion of mucochloric acid, and coating the mixture on a transparent support.

FRANK L. WHITE.. 

